Dimerization of conjugated dienes

ABSTRACT

CONJUGATED DIENES, SUCH AS BUTADINE, ARE DIMERIZED TO SUBSTITUTED CYCLOHEXENES, SUCH AS 4-VINYLCYCLOHEXANE, BY CONTACTING THE DIENE WITH A CATALYST FORMED FROM (I) A DINITROSYLIRON HALIDE AND (II) AN ORGANOLUMINUM HALIDE SUCH AS DIETHYLALUMINUM CHLORIDE, AN ALKALI METAL HYDRIDE, OR COMPLEX HYDRIDES OF ALKALI METALS AND BORON OR ALUMINUM.

United States Patent 3,655,793 DIMERIZATION 0F CONJUGATED DIENES CharlesL. Myers, Parkersburg, W. Va., assignor to Phillips Petroleum Company NoDrawing. Continuation-impart of application Ser. No. 889,748, Dec. 31,1969. This application Dec. 10, 1970,

Ser. No. 97,016

Int. Cl. C07c 3/60 U.S. Cl. 260-666 B 16 Claims ABSTRACT OF THEDISCLOSURE Conjugated dienes, such as butadiene, are dimerized tosubstituted cyclohexenes, such as 4-vinylcyclohexene, by contacting thediene with a catalyst formed from (I) a dinitrosyliron halide and (II)an organoaluminum halide such as diethylaluminum chloride, an alkalimetal hydride, or complex hydrides of alkali metals and boron oraluminum.

This is a continuation-in-part of U.S. application Ser. No. 889,748,filed Dec. 31, 1969, now abandoned.

This invention relates to the dimerization of conjugated dienes. Inanother aspect, it relates to catalysts useful in the dimerization ofconjugated dienes.

Various processes have been developed for the dimerization of conjugateddienes. However, some of these processes yield, besides the desireddimers, a wide variety of other products which substantially reduce theultimate yield of the desired dimer. Since the conjugated diene dimersare useful as intermediates for the production of a large number ofcompounds, a process leading to the production of these dimers in largeyields would be very valuable.

Accordingly, it is an object of this invention to provide a process forthe dimerization of conjugated dienes. It is a further object of myinvention to provide a novel catalyst system.

Other objects, aspects and advantages of this invention will be readilyapparent to one skilled in the art upon consideration of the followingdisclosure and appended claims.

It now has been discovered that conjugated dienes can be dimerized bycontacting the diene with a catalyst consisting essentially of thatformed from (I) a dinitrosyliron halide and (II) a reducing agent whichis an organo-aluminum halide, an alkali metal hydride, or a complexhydride of an alkali metal plus boron or aluminum. It also has beendiscovered that the diene can be present before the dinitrosylironhalide comes in con tact with the organo-alurninum halide, the alkalimetal hydride, or the complex hydride. Thus, my catalyst can be preparedin the reactor used for the dimerization of the diene, and the presenceof additional ligand-forming compounds is not required.

The conjugated dienes that are employed in my invention are representedby the formula:

wherein R is hydrogen, methyl or ethyl. Thus, conjugated dienes that areemployed in this invention can range from 4 to 8 in the number of carbonatoms per molecule.

Specific examples of these dienes are: 1,3-butadiene,

isoprene, 2,3-dimethyl 1,3 butadiene, 2-ethyl-1,3-butadiene, 2-methy1 3ethyl 1,3 butadiene, 2,3-diethyl- 1,3-butadiene, and mixtures thereof.

In accordance with my invention, conjugated dienes are dimerized toproduce substituted cyclohexenes represented by the formula:

wherein R is as previously defined.

Specific examples of these substituted cyclohexenes include4-vinylcyclohexene, 1,4-dimethyl 4 vinylcyclohexene, 2,4 dimethyl 4vinylcyclohexene, 1,2,4-trimethyl 4 isopropenylcyclohexene,1,4-diethyl-4-vinylcyclohexene, l-methyl 2,4 diethyl 4isopropenylcyclohexene, l,2,4-triethyl-4-( l-ethylvinyl)cyclohexene, 2-methyl-4-vinylcyclohexene, and the like, and mixtures thereof.

The dinitrosyliron halides that are employed in my invention can berepresented by the formula Fe(NO) X wherein X is a halogen andpreferably is chlorine, bromine, or iodine. Specific dinitrosylironhalides are dinitrosyliron chloride, dinitrosyliron bromide, anddinitrosyliron iodide. Some dinitrosyliron halides are believed to existin dimeric and possibly other polymeric forms. However, for purpose ofthis invention, particularly in regard to molar calculations, thedinitrosyliron halides are considered to be monomeric having but oneatom of iron per molecule.

In accordance with my invention, the organoaluminum halides arerepresented by the formula R AlX wherein R is a monovalent hydrocarbonradical having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, Xis as previously defined, x and y are integers of at least 1, and thesum of x and y is 3.

Specific examples of these organoaluminum halides include methylaluminumdichloride, dimethylaluminum chloride, ethylaluminum dibromide,diethylaluminum chloride, vinylaluminum dichloride, isopropylaluminumdibromide, dibutylaluminum iodide, dihexylaluminum chloride,phenylaluminum dibromide, dibenzylaluminum chloride, para-tolylalurninumdichloride, dodecylaluminum dibromide, dieicosylaluminum chloride, andmixtures thereof such as methylaluminum sesquichloride, ethylaluminumsesquichloride, and the like.

Specific examples of alkali metal hydrides include lithium hydride,sodium hydride, potassium hydride, rubidium hydride, and cesium hydride.

Specific examples of applicable complex hydrides of alkali metals andboron or aluminum include lithium aluminum hydride, lithium borohydride,sodium aluminum hydride, sodium borohydride, potassium borohydride,rubidium aluminum hydride, cesium borohydride, and the like.

Of course, it is feasible and suitable to use combinations, wheredesired, of an alkali metal hydride plus a complex hydride, or of analkali metal hydride with an organoaluminum halide, or other admixture,in addition to using the nitrosyliron compound as hereinbeforedescribed.

Preferably, a diluent or solvent, substantially nonreactive or veryslowly reactive with the other components,

can be employed. When an organo-aluminum halide is employed as thereducing agent, a saturated or aromatic hydrocarbon such as pentane,heptane, cyclohexane, benzene, toluene, or xylene can be employed. Othersuitable diluents or solvents are the halogenated aliphatic hydrocarbonssuch as tetrachloroethylene, or the halogenated aromatic hydrocarbonssuch as chlorobenzene. The saturated or aromatic hydrocarbon, or thehalogenated aromatic hydrocarbon, preferably should contain from 2 to 8carbon atoms per molecule. Mixtures, of course, can be employed ifdesired.

When the reducing agent is an alkali metal hydride or a complex hydrideof an alkali metal and boron or aluminum, it is preferable to employ asolvent which will substantially dissolve or disperse the hydride. Sucha solvent should be one which either does not react with the hydride orelse reacts with the hydride sufficiently slowly that the major amountof the hydride is enabled to function as a reducing agent in my processfor the more reactive dinitrosyliron halide. The preferred solvents forthe alkali metal hydrides and alkali metal aluminum hydrides are theethers of 2 to 8 carbon atoms per molecule, such as tetrahydrofuran,dioxane, dimethyl ether, diethyl ether, dibutyl ether, and the like, andmixtures thereof.

The preferred solvents for the alkali metal borohydrides are the loweralcohols, of from 1 to 8 carbon atoms per molecule, such as methylalcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, octyl alcohol,monomethyl ether of ethyene glycol, and the like, including mixturesthereof. Alsoapplicable are ethers, e.g., ethers of 2 to 8 carbon atomsper molecule such as those described above as solvents for the alkalimetal hydrides and alkali metal aluminum hydrides.

If desired, particularly when mixtures of reducing agents are utilized,such as an alkali metal hydride plus a complex hydride, a mixture ofdiluents of sufficiently little reactivity with the reducing agentspresent can be employed.

In the process of my invention, the mole ratio of (II) reducing agent to(I) dinitrosyliron halide generally ranges from 0.01:1 to 20:1,preferably from 1:1 to 10:1. The mole ratio of diene to dinitrosylironhalide generally ranges [from 50:1 to 50,000:l, preferably from 500:1 to5,000z1.

Although it can vary considerably, the reaction temperature generallyranges from --40 to 120 C., preferably from 10 to 70 C. The reactiontime can vary over a wide range depending in part on the reactiontemperature, but generally ranges from 2 minutes to 48 hours, preferablyfrom 10 minutes to 24 hours. The reaction pressure generally is withinthe range of from to 300 p.s.i.g., preferably from 0 to 100 p.s.i.g.

The dimerization of the diene reactant can be carried out in a batchprocess, in a continuous process, or in a semi-continuous processwherein the diene is intermittently charged as needed to replace thatalready dimerized. At the end of the dimerization reaction, the dimercan be recovered by any conventional means known to the art such asdistillation, extraction, adsorption, and the like.

The process of my invention, unlike the processes of some catalyticdimerization processes, converts the dienes to substituted cyclohexenes,e.g., butadiene to 4-vinylcyclohexene, without the production ofsubstantially any other products. In addition to this feature of verysubstantial ultimate yields of the dimer, high conversion and highproductivity also can be realized by the process of my invention.:Furthermore, the reaction is carried out at mild temperatureconditions, thereby avoiding thermal polymerization and/ or cracking orother deleterious effects on the dimer product.

The advantages of my invention are further illustrated by the followingexamples. The reactants, proportions and other specific conditions arepresented as being typical and should not be construed to limit theinvention unduly.

4 EXAMPLE I In a Pyrex aerosol tube, 0.02 g. (gram) of dinitrosylironchloride was charged and the tube was evacuated. Ten ml. (milliliters)of chlorobenzene were added and the tube again was evacuated and cooled.After the addition of 13.91 g. of 1,3-butadiene, the tube again wascooled and 0.44 ml. of 1.25 M diethylaluminum chloride in heptane wereadded, followed by the addition of 3 ml. of chlorobenzene. The reactionmixture was stirred and maintained at a temperature of 20 C. for 16hours. The mixture then was cooled and 10 ml. of pentane were injected.The tube was opened and 25 ml. of 1 M hydrochloric acid were added. Theorganic layer, with 10 ml. of additional pentane, was separated andwashed with water.

Gas chromatographic analysis of the washed organic layer showed that13.3 g. of 4-vinylcycolhexene were produced, representing a 96 percentconversion of butadiene to 4-vinylcyclohexene. No other volatile productwas detected.

This run demonstrates that substantially quantitative yields of thedimer can be obtained according to the process of my invention, as wellas high conversion and productivity.

EXAMPLE II 'In a ml. Pyrex aerosol tube in a dry-box were placed 0.02 g.(0.1 millimole) of dinitrosyliron chloride and 0.02 g. (0.5 millimole)of lithium aluminum hydride. The tube was evacuated and cooled in ice,and 9.26 (171 millimoles) of 1,3-butadiene were added. The tube wascooled in ice-salt, and 10 ml. of tetrahydrofuran were added, afterwhich the mixture was stirred at 40 C. for 19 hours. The tube then wascooled and vented, and 25 ml. of 1 M hydrochloric acid and 15 ml. ofpentane were added, and the organic layer recovered as before.

Gas chromatographic analysis of the organic layer showed that 37millimoles of 4-vinylcyclohexene were produced, representing a 43percent conversion of butadiene to 4-vinylcyclohexene. No other volatileproduct was detected, and only 0.06 g. of non-volatile residue remainedupon evaporation of solvent from the organic layer.

This run further demonstrates the effectiveness of the invention using adinitrosyliron halide together with a complex hydride to produce a dimerwith little or no other product formation.

EXAMPLE III In a 110 ml. Pyrex aerosol tube in a dry-box were placed0.02 g. (0.1 millimole) of dinitrosyliron chloride and 0.02 g. (0.5millimole) of sodium borohydride. The tube was evacuated and cooled inice, and 12.90 g. (239 millimoles) of 1,3-butadiene were added. The tubewas cooled in ice-salt at -15 C., and 10 ml. of nitrogensaturated ethylalcohol were added. The tube was warmed gradually, with stirring,whereupon a sudden exotherm was observed when the temperature of thebath reached 27 C. The pressure jumped from less than 20 p.s.i.g. to 50p.s.i.g., then gradually subsided to less than 20 p.s.i.g. at 29 C. Themixture then was stirred for 30 minutes at 40 C., after which the tubewas cooled in ice and 6.49 g. millimoles) of additional 1,3-butadienewere added. The tube again was warmed with stirring, but no exotherm wasobserved. The mixture was stirred for 17 hours at 43 C. and then cooled,after which 20 ml. of pentane were injected. The tube then was opened,and 25 ml. of 1 M hydrochloric acid and 10 ml. of pentane were added.The organic layer was separated and washed with water.

Gas chromatographic analysis of the washed organic layer showed that 7.3g. of 4-vinylcyclohexene were produced, representing a 38 percentconversion of the total butadiene charged. No other volatile product wasdetected, and no non-volatile residue remained upon evaporation ofsolvent from the organic layer.

This run further demonstrates the eifectiveness of the invention using adinitrosyliron halide together with another complex hydride to produce adimer with little or no other product formation.

EXAMPLE IV In a 110 ml. Pyrex aerosol tube in a dry-box were placed 0.02g. (0.1 millimole) of dinitrosyliron chloride and 0.02 g. (0.5millimole) of sodium borohydride. The tube was evacuated and cooled inice, after which 12.96 g. (240 millimoles) of 1,3-butadiene were added.The tube was cooled in ice-salt, and ml. of ethyl alcohol were added.The mixture then was stirred in a water bath at 20 C. for 16 hours. Theresulting mixture was cooled in ice and 20 ml. of pentane were injected.The tube was opened and 25 ml. of 1 M hydrochloric acid were added. Theorganic layer was separated and washed with water.

Gas chromatographic analysis of the washed organic layer showed that 2.8g. of 4-vinylcyclohexene were produced, representing a 21 percentconversion of butadiene charged. No other volatile product was detected.

This run further demonstrates the effectiveness of the invention using adinitrosyliron halide together with a complex hydride to produce a dimerwith little or no other product formation.

Although this invention has been described in considerable detail, itmust be understood that such detail is for the purpose of illustrationonly and that many variations and modifications can be made by oneskilled in the art without departing from the scope and spirit thereof.

I claim:

1. A process for the dimerization of at least one conjugated dienewherein R is hydrogen, methyl, or ethyl, which comprises contacting saidat least one diene under dimerization conditions with a catalyst from(1) a dinitrosyl iron halide together with (II) an alkali metal hydride,a complex bydride of an alkali metal and boron or aluminum, or anorganoaluminum halide represented by the formula R AlX wherein R is amonovalent hydrocarbon radical having 1 to 20 carbon atoms, X is ahalogen, and x and y are integers of at least 1 such that the sum of xplus y is 3.

2. A process according to claim 1 wherein said (H) is an organoaluminumhalide and wherein said dinitrosyliron halide is contacted with saiddiene prior to contact with said organoaluminum halide.

3. A process according to claim 1 wherein said diene is 1,3-butadiene orisoprene.

4. A process according to claim 1 wherein said diene is 1,3-butadiene.

5. A process according to claim 1 wherein said dinitrosyliron halide isdinitrosyliron chloride, dinitrosyliron bromide or dinitrosylironiodide.

6. A process according to claim 1 wherein said dinitrosyliron halide isdinitrosyliron chloride.

7. A process according to claim 1 wherein R has 1 to 6 carbon atoms andX is chlorine, bromine or iodine.

8. A process according to claim 1 wherein said organoaluminum halide isdiethylaluminum chloride.

9. A process according to claim 1 wherein said contacting is carried outat a temperature ranging from 40 to C., under a pressure ranging from 0to 300 p.s.i.g., and for a time ranging from 2 minutes to 48 hours.

10. A process according to claim 1 wherein the mole ratio of said dieneto said dinitrosyliron halide ranges from 50:1 to 50,000:1 and the moleratio of said organoaluminum halide to said dinitrosyliron halide rangesfrom 0.01:1 to 20:1.

11. A process according to claim 1 wherein at least one substitutedcyclohexene is produced having the for mula wherein R is as defined inclaim 1.

12. A process according to claim 1 wherein 4-vinylcyclohexene isproduced.

13. The process according to claim 1 wherein further is employed adiluent of from 2 to 8 carbon atoms per molecule selected from the groupconsisting of saturated hydrocarbons, aromatic hydrocarbons, andhalogenated hydrocarbons, and mixtures thereof.

14. A process according to claim 1 wherein is employed a mole ratio ofsaid at least one diene to said (I) dinitrosyliron halide of from 50:1to 50,000: 1, and wherein said contacting is carried out at atemperature of from 40 to +120 C., under a pressure of from 0 to 300p.s.i.g., and during a reaction time of from 2 minutes to 48 hours.

15. A process according to claim 14 wherein said (I) is dinitrosylironchloride, and said (II) is lithium aluminum hydride, or sodiumborohydride, and said at least one diene is 1,3-butadiene.

16. A process according to claim 14 wherein further is employed adiluent selected from ethers of from 2 to 8 carbon atoms per moleculewith said alkali metal hydride or said alkali metal aluminum hydride,and lower alcohols of from 1 to 8 carbon atoms per molecule or ethers offrom 2 to 8 carbon atoms per molecule with said alkali metalborohydride.

References Cited UNITED STATES PATENTS 3,377,397 4/1968 Maxfield 260-666B 3,446,862 5/1969 Menapace et al. 260-666 B 3,436,431 4/1969 Candlin eta1. 260-666 B 3,446,861 5/1969 Menapace et al. 260-666 B 3,448,129 6/1969 Maxfield 260-666 B 3,457,319 7/1969 Olechawski et a1. 260-666 BDELBERT E. GANTZ, Primary Examiner V. OKEEFE, Assistant Examiner U.S.Cl. X.R. 252-429 N, 431 P

